1. Field of the Invention
The present invention is related to a method for improving physical characteristics of cured container coating compositions.
2. Description of the Related Art
In the area of coating compositions for packaging containers, coatings intended for use in containers used in the food and beverage industries generally are expected to meet a number of requirements in order to be commercially acceptable. The coating should adhere well to the base metal and should possess flexibility, extensibility and adhesion characteristics so as to withstand the processing of the container itself. The coating must be able to resist heat which is encountered during processing of the container and its contents. Additionally, the coating itself should not affect the taste of a food or beverage which is put into the container.
Container coatings are subjected to steam processing and prolonged bake cycles. Steam processing often causes a defect in container coatings called blush, which is a haziness in the film thought to be caused by absorption of water. Blush is particularly evident with container coatings that are subjected to high temperature and high humidity conditions during steam processing.
It is desirable that container coating compositions provide cured films that are resistant to defects caused by steam processing. These defects include water spotting and blush, as well as decreased solvent resistance and gloss retention.
Container coatings containing hydroxyl functional polymeric resins demonstrate various disadvantages such as poor resistance to blush and water spotting, diminished solvent resistance and poor gloss retention, upon exposure to steam processing.
An object of the present invention is to provide a coating composition and method for improving resistance of container films to degradation upon exposure to steam processing. A further object of the present invention is to provide a container coating composition comprising carbamate functional compounds and an article coated with said coating composition.